Interpretive Summary: Oxygen Radical Absorbance Capacity Assay (ORAC) is now widely utilized to measure the in vitro antioxidant capacity of biological and food samples. Recently a modified method using a solubility enhancer was developed for lipid soluble (lipophilic) antioxidant capacity in addition to the hydrophilic (water soluble) assay for analysis of food samples. A substantial body of research indicates that dietary antioxidants may play a role in the prevention of many diseases including atherosclerosis, cancer and diabetes. Thus, in order to evaluate the impact of dietary antioxidants, a total value of antioxidants consumed must be estimated. Total antioxidant capacity was measured on more than 500 samples, which were comprised of 85 different fruits, nuts and vegetables sampled as part of USDA's National Food and Nutrient Analysis Program from four different areas of the U.S. and in two different seasons. Food samples were extracted with a lipophilic solvent and then with a hydrophilic solvent. Extracts were processed and diluted to the proper concentration and were measured for lipophilic and hydrophilic antioxidant capacity using a 48-well plate reader. Antioxidant capacity varied significantly in different foods. Values for the water soluble antioxidants ranged from 4.43 ± 1.11 to 2640.83 ± 42.31 units of activity expressed as 'mol Trolox equivalents (TE)/g dry weight in pine nuts and cinnamon, respectively; whereas lipid soluble antioxidant concentrations ranged from 1.00 ± 0.06 to 1611 ± 20.13 'mol TE/g weight in cloves and honeydew melon, respectively. Complete data on lipophilic and hydrophilic antioxidants was obtained. These data covered most common fresh foods in the U.S. market. These results will be used to calculate daily intake of total antioxidants and may help to evaluate the potential health benefit of these foods.

Technical Abstract:
Oxygen Radical Absorbance Capacity Assay (ORAC) is now widely utilized to measure the in vitro antioxidant capacity of biological and food samples. Recently a modified method using randomly methylated ß-cyclodextrin as a solubility enhancer was developed for lipophilic ORAC. From our research results, we find that in order to measure the total antioxidant capacity of a given sample, lipophilic and hydrophilic components must be measured separately and then combined. A substantial body of research indicates that dietary antioxidants may play a role in the prevention of many diseases including atherosclerosis, cancer and diabetes. Thus, in order to evaluate the impact of dietary antioxidants, a total value of antioxidants consumed must be estimated.
Objective: Measure total ORAC, (lipophilic and hydrophilic ORAC) on more than 500 samples, which were comprised of 85 different fruits, nuts and vegetables sampled as part of USDA's National Food and Nutrient Analysis Program from four different areas of the U.S. and in two different seasons.
Methods and Materials: Food samples were extracted with a lipophilic solvent (hexane/ dichloromethane) and then by a hydrophilic solvent (acetone/water/acetic acid) in the Dionex ASE-200 accelerated solvent extractor. Extracts were processed and diluted to the proper concentration and were measured for lipophilic and hydrophilic ORAC using a 48-well plate reader.
Results: Antioxidant capacity (ORAC) varied significantly in different foods. Hydrophilic ORAC values ranged from 4.43 ± 1.11 to 2640.83 ± 42.31 'mol Trolox equivalents (TE)/g dry weight in pine nuts and cinnamon, respectively; whereas lipophilic ORAC ranged from 1.00 ± 0.06 to 1611 ± 20.13 'mol TE/g weight in cloves and honeydew melon, respectively. Lipophilic ORAC as a percentage of the Total ORAC (Hydrophilic plus Lipophilic ORAC) ranged from 0.35% to 51% in black plums and cloves, respectively.
Significance: Complete data on lipophilic and hydrophilic ORAC was obtained. These data covered most common fresh foods in the U.S. market. These results will be used to calculate daily intake of total antioxidants and may help to evaluate the potential health benefit of these foods.